Field of the Disclosure
This disclosure relates generally to equipment for recovering fluid, which may be a liquid and/or a gas, from within the earth. More particularly, it relates to an oil and gas production pump. Still more particularly, this disclosure relates to an apparatus and system for rotating a polish rod/sucker rod that is reciprocated by an arm on an oil and gas production surface pump.
Background to the Disclosure
At various production wells, oil and gas is extracted using one of several types of reciprocating pumps. In a common application, the pump includes a series or “string” of sucker rods extending below the surface of the earth within a stationary series or string of production tubing. The production tubing is positioned within a wellbore casing. An “insert pump” or a “down-hole pump” (or “downhole pump”) is coupled to the end of the sucker rod string and is positioned adjacent the end of the production tubing string pump. Reciprocation of the sucker rod string acting on the down-hole pump draws fluid, e.g. oil or gas, into the production tubing and raises the fluid to the surface of the earth. The sucker rod is coupled to a means of reciprocation, such as a pivoting or “walking beam” on a pumping jack. A polished rod extends upward from the sucker rod string to a carrier bar coupled by cables to one end of the surface unit's walking beam.
For a longer service life, the sucker rod and polished rod are rotated relative to the stationary production tubing by the action of a rod rotator located near the intersection of the polished rod and the carrier bar. To insure the rods rotate in only one direction, conventional rod rotators include a ratchet mechanism. A conventional ratchet mechanism has a minimum angle through which it must be rotated so that the rod will progressively rotate in the appropriate direction rather than just oscillate back-and-forth. Some conventional ratchet mechanisms include an annular ring with internal teeth, circumferentially spaced at even intervals and one or more pawls that rotate within the annular ring, sequentially engaging the teeth. The pawl is coupled for rotation with an axial that drives the rotation of the polished rod. The angular spacing of the teeth on the ring determine the smallest angle of rotation that will allow the pawl to progress and hold a new position, allowing the polished rod to progress to a new position. Any smaller rotation of the axial and pawl allows the pawl to return to its former resting place. As an example, for an annular ring having 24 teeth, the pawl and axle must rotate through a minimum angle of 15° (i.e. 360°/24) in order to progress to the next tooth to hold the pawl and axle in a new angular position and ultimately to rotate and hold the polished rod in a new angular position. The apparatus and system disclosed below offer an improved rod rotator intended to overcome various deficiencies of the prior art.